My drivers have no write routines implemented. You want to
know why? My intention was to have USB drivers for UHCI, OHCI
and EHCI controllers in my tiny boot manager. The space to install
the boot manager without the need of a partition is very limited.
So there was no space left for write routines.

Are there plans to add write support in the future

It's in my mind, but there are no fix plans.

The boot manager detect's my usb cdrom, but booting hangs

USB CD/DVD drives are not supported.

My USB keyboard does not work when I booted from USB

USB keyboards are not supported by my drivers. When you boot Linux or Windows,
then your keyboard will work again when those operating systems are taking
control over the USB hardware.

Can I use my USB PC-Card (PCMCIA CardBus) to boot from USB

Yes, with the pcmcai version of the boot manager

I want to install the boot manager from my USB device, but I cannot choose my internal hard disk

The problem with installing on the internal (in this case the second) hard disk
with the installer
is, that the installer imports the partitions from the usb device and
thinks this are the partitions of the first hard disk. When the boot
manager boot's later from the real hard disk then the imported partitions are
not correct. You see the problem? Sure it would be possible to add an option to
handle this situation, but there are so many other ways to install the boot manager, that
there are no plans to add this feature to the installer (except, many people request this feature).

I use plpbt.bin and it forgets my settings

You have to configure plpbt.bin with plpcfgbt. All changes you make within
the boot manager menu are only valid until you reboot. The changes are not saved.

I cannot boot from my SATA CD/DVD drive

SATA CD/DVD drives are not supported. Only IDE CD/DVD drives are working.